1. Field of the Invention
The present invention relates to fluid pressure devices which can be used either as pumps or motors.
2. Prior Art
Various fluid devices utilizing a swash plate principle of actuation have been advanced. Some of these have attempted to provide load reducing couplings for the pistons and the cylinders. Examples of such connections are shown in U.S. Pat. Nos. 2,157,692 to Doe et al; 3,245,354 to Gregor; and 2,146,133 to Tweedale.
U.S. Pat. No. 3,479,963, issued to Randa et al, and U.S. Pat. No. 3,246,577 issued to MacIntosh show devices for resiliently biasing a rotating cylinder carrier against a valving surface.
Other swash plate fluid devices have mounted the plates on the shafts with limited pivotal movement being provided. Examples of this type of drive for the variable cam or swash plate are shown in U.S. Pat. Nos. 2,095,316 issued to Davis; 1,118,799 issued to Prott; and 3,319,874 issued to Welsh et al. Further showings occur in U.S. Pat. Nos. 2,465,510 issued to Bonnafe; 3,292,554 issued to Hessler; and 2,231,100 issued to Wahlmark.
Additionally, U.S. Pat. No. 2,661,695 discloses, in FIGS. 3 and 6, an arrangement for minimizing noise by precharging or prefilling the cylinders as the units are rotated from the low to the high pressure ports. However, a very complex arrangement is disclosed to accomplish this end, and the structure is much different from that utilized in the present device. U.S. Pat. No. 3,699,845, issued to Ifield, shows a pump which has a port plate that has small passageways which are used to avoid rapid changes in pressure in the passageways associated with the port as the pump is operated. The small passageways permit limited flow before full communication of the ports and associated passageways.